A staging system is a standard way for the cancer care team to sum up how far a cancer has spread. The most common systems used to describe the stages of eye melanomas are the American Joint Committee on Cancer (AJCC) TNM system and the system used by the Collaborative Ocular Melanoma Study (COMS) group.

AJCC TNM staging system for melanoma of the eye

The TNM system is based on 3 key pieces of information:

T describes the size of the main (primary) tumor and/or whether it has invaded into nearby structures.

N describes whether the cancer has spread to nearby (regional) lymph nodes (bean-sized collections of immune system cells throughout the body).

M indicates whether the cancer has metastasized (spread) to other organs of the body. (The most common site of eye melanoma spread is the liver.)

Numbers or letters appear after T, N, and M to provide more details about each of these factors:

The letter X means “cannot be assessed” because the information is not available.

Most eye melanomas start in the uvea, which includes the iris, ciliary body, and choroid (see “What is eye cancer?”). The T categories for iris melanomas are different from the T categories for ciliary body and choroidal melanomas. But the N and M categories are the same for melanomas in all 3 parts of the uvea.

T categories for iris melanoma

TX: The primary tumor cannot be assessed; information not known.

T0: No evidence of a primary tumor.

T1: Tumor is only in the iris.

T1a: The tumor is only in the iris and touches 1/4 or less of the iris.

T1b: The tumor is only in the iris and touches more than 1/4 of the iris.

T1c: The tumor is only in the iris and is causing an increase in the eye pressure (glaucoma).

T2: Tumor has grown into the ciliary body or choroid (or both).

T2a: Tumor has grown into the ciliary body and/or choroid and is causing glaucoma.

T3: Tumor has grown into the ciliary body and/or choroid and into the sclera.

T3a: Tumor has grown into the ciliary body and/or choroid and into the sclera and is causing glaucoma.

T4: Tumor extends outside the eyeball.

T4a: The part of the tumor that is outside the eyeball is 5 millimeters (mm) — about 1/5 of an inch — or less across in size.

T4b: The part of the tumor that is outside the eyeball is greater than 5 mm (about 1/5 of an inch) across in size.

T categories for ciliary body and choroidal melanoma

TX: The primary tumor cannot be assessed; information not known.

T0: No evidence of a primary tumor.

T1: A T1 tumor is either:

No more than 3 millimeters (mm) deep and no more than 12 mm across, OR

From 3.1 to 6 mm deep and no more than 9 mm across

T1a: The T1-size tumor is not growing into the ciliary body or growing outside the eyeball.

T1b: The T1-size tumor is growing into the ciliary body.

T1c: The T1-size tumor is not growing into the ciliary body but is growing outside of the eyeball. The part of the tumor that is outside the eyeball is 5 mm (about 1/5 of an inch) or less across.

T1d: The T1-size tumor is growing into the ciliary body and also outside of the eyeball. The part of the tumor that is outside the eyeball is 5 mm (about 1/5 of an inch) or less across.

T2: A T2 tumor is:

No more than 3 mm deep and from 12.1 to 18 mm across, OR

From 3.1 to 6 mm deep and 9.1 to 15 mm across, OR

From 6.1 to 9 mm deep and no more than 12 mm across

T2a: The T2-size tumor is not growing into the ciliary body or growing outside the eyeball.

T2b: The T2-size tumor is growing into the ciliary body.

T2c: The T2-size tumor is not growing into the ciliary body but is growing outside the eyeball. The part of the tumor that is outside the eyeball is 5 mm (about 1/5 of an inch) or less across in size.

T2d: The T2-size tumor is growing into the ciliary body and also outside the eyeball. The part of the tumor that is outside the eyeball is 5 mm (about 1/5 of an inch) or less across in size.

T3: A T3 tumor is:

From 3.1 to 6 mm deep and between 15.1 and 18 mm across, OR

From 6.1 to 9 mm deep and between 12.1 and 18 mm across, OR

From 9.1 to 12 mm deep and 18 mm or less across, OR

From 12.1 to 15 mm deep and 15 mm or less across

T3a: The T3-size tumor is not growing into the ciliary body and is not growing outside the eyeball.

T3b: The T3-size tumor is growing into the ciliary body.

T3c: The T3-size tumor is not growing into the ciliary body but is growing outside the eyeball. The part of the tumor that is outside the eyeball is 5 mm (about 1/5 of an inch) or less across in size.

T3d: The T3-size tumor is growing into the ciliary body and also outside the eyeball. The part of the tumor that is outside the eyeball is 5 mm (about 1/5 of an inch) or less across in size.

T4: A T4 tumor is:

Greater than 15 mm deep and any width, OR

Greater than 18 mm across and any depth, OR

Between 12.1 and 15 mm deep and between 15.1 and 18 mm across

T4a: The T4-size tumor is not growing into the ciliary body or growing outside the eyeball.

T4b: The T4-size tumor is growing into the ciliary body.

T4c: The T4-size tumor is not growing into the ciliary body but is growing outside the eyeball. The part of the tumor that is outside the eyeball is 5 mm (about 1/5 of an inch) or less across in size.

T4d: The T4-size tumor is growing into the ciliary body and also outside the eyeball. The part of the tumor that is outside the eyeball is 5 mm (about 1/5 of an inch) or less across in size.

T4e: The tumor can be any size. It is growing outside the eyeball and the part of the tumor that is outside the eyeball is greater than 5 mm across.

N categories for iris, ciliary body, and choroidal melanomas

NX: Lymph nodes cannot be assessed.

N0: Cancer has not spread to nearby lymph nodes.

N1: Cancer has spread to nearby lymph nodes.

M categories for iris, ciliary body, and choroidal melanomas

M0: Cancer has not spread to distant parts of the body.

M1: Cancer has spread to distant parts of the body.

M1a: The largest area of cancer spread is 3 centimeters (cm) — a little over an inch — across or smaller.

M1b: The largest area of cancer spread is between 3.1 and 8 cm across (8 cm is a little over 3 inches).

M1c: The largest area of cancer spread is 8.1 cm or more across.

Stage grouping

To assign an overall stage, the T, N, and M categories are combined in a process called stage grouping. The stages are described by Roman numerals from I (the least advanced) to IV (the most advanced). Some stages are further divided with letters.

The TNM system is very detailed, but in practice many doctors use the simpler staging system devised by the COMS group, which has done most of the clinical research on how to treat intraocular melanoma. This system divides eye melanomas into small, medium, and large:

Small: Between 1 mm and 3 mm in height and between 5 mm and 16 mm across

Medium: Between 3.1 mm and 8 mm in height and no more than 16 mm across

Large: More than 8 mm in height or more than 16 mm across

Staging of intraocular lymphoma

Intraocular lymphoma does not have its own staging system. These cancers may be staged using the system for other non-Hodgkin lymphomas, which is described in our document Non-Hodgkin Lymphoma.

Unlike eye melanomas, the size of the tumor is usually not a major factor in determining the treatment options for eye lymphomas. Instead, treatment options are generally based on the type of lymphoma, as well as on whether the lymphoma is limited to the eye or is also in other areas of the body.